The Imperial Garden in Madison is both a good Chinese restaurant AND a gas station.
Years ago, in Schenectady there was a Wetson’s, probably the worst fast food ever to appear on the face of the Earth. Someone took the building and turned it into a Korean restaurant, but it still looked like a fast food place. They didn’t stay in business long.
Some fine cheeseburgers and fries at the Oklahoma Heart Hospital cafeteria.
Eat & Get Gas. 
The one in Copenhagen was accessible from the street, with another door between the the restaurant and the embassy grounds, as I recall. The street door was kept barred during the day, and the door to the embassy grounds was barred after embassy business hours. It was likely a local concession business. Also, I carried a diplomatic passport at the time. 
FWIW, most embassies have pretty mediocre lunch service. The locals in the Belgrade embassy had their own lunch room, where they served a killer bean soup with a hunk of local bread.
One of the best sushi places in Portland is in a food cart here in my neighborhood.
The best battered halibut in Alaska is in a small greasy spoon called The White Spot Cafe in Anchorage. It’s been in existence since at least the 60s, when it was a very narrow space in an opening between two other buildings where I used to get the best homemade burgers and fresh fries of my misspent yoot.
Best dry rub ribs were in a floating restaurant on the Danube River in Vienna.
In Woodland Hills CA, around the corner from my old office, there is a Sandwich Shop in the Chevron Gas Staion.
IN THE GAS STATION!!
I loved this place. I go there whenever I am back in SoCal. They have the best tomato soup and the best cream of mushroom soup EVER! They have a delicious vegetarian paninni. I’m not a vegetarian and I still order it every time.
Aguanga, CA… Anyone know it?
The best pizzeria I’ve been to was in New Orleans. They’re now in River Ridge, presumably due to Katrina flood damage.
These days, many hospitals, even smaller ones, have cafeterias that are more like station restaurants: Salad station, sandwich station, maybe japanese and vegetarian stations, grill, etc. Great food and subsidized pricing!
I’ve been in some good diners in what had once been someone’s house, or at least were purposely constructed to appear so.
I recall a few of those around the Gettysburg area…
Here in Portland Maine there’s been a small house/restaurant on Forest Ave for maybe 20+ years. It’s called Bre-Lu. People think it’s some French reference to the house, but it’s really just short for breakfast and lunch. Heh. Go there for a great brunch!
Moved to Texas four years ago from Los Angeles and have been missing falafel ever since. In the food court at the mall there’s a restaurant called Potato Club which also serves some middle eastern food: falafel, gyros, etc. I didn’t try it for months because after all, the food court at the mall? The Potato Club? Finally I broke down.
It’s wonderful! I had tried two “Greek” restaurants in the Austin area and their falafel was inedible. The Potato Club does it right, even makes a nice lookig platter with hummus, tahini sauce, Greek salad, pita cut into wedges, even puts paprika and olive oil and a Greek olive on the hummus. Never expected that! They have a tendency to overcook the falafel but I just tell them I like it less crispy and they are glad to oblige. Most of the folks working there are hispanic, which makes it even more interesting. I just regret all those falafel-less months that went by before I decided to give it a try.
There is a great sushi joint in Carson City, NV between a thrift store and an auto repair place. Its run by two guys from Mexico. I’ve been eating there so long and often that I don’t need to order a thing. They just make it a hand it over.
The absolute, hands-down best clam chowder I’ve ever had - and understand I’ve tried it in a dozen states including most of New England, England, some of the most vaunted seafood restaurants on earth (both hoity-toity and ‘real’) and everywhere else I’ve been assured of the best - …
…was Harrah’s casino-floor restaurant in Reno. No sh*t.
I mentioned in another thread that some of the best food I had was in a shack next to the river-boat stop in Bangkok. Stunning papaya salad. But then that is thai food in thailand so perhaps not so unexpected.
The best Chinese food I’ve ever had (and I’ve eaten it world-wide) is at the “Eastern Bamboo” in Darlington, Co.Durham. For those not aware it is a quiet little north-eastern town, famous for the birth of the railway but not a huge amount else. Why there is a stunning chinese restaurant there I simply don’t know.
I’ve eaten there for nigh on 40 years since being a kid and never had a bad meal. Their chili-chicken-wings are on my death row lunch menu and their Cantonese fillet steak is worth starting a regional conflict for. I tip my hat to the Ma family. Their trip advisor link is pretty much universally brilliant which is something of a first.
I had excellent Indian food in Vang Vieng, Laos, in a space that most closely resembled, to my western eyes, a two-car garage. I remember a Bollywood movie was playing on a tiny TV mounted on the wall.
Some years ago there was a seafood restaurant in Florida, somewhere on the Tamiami trail, busy street, amongst all the fast food places, the chains, things like Applebees and TGI Fridays, endless commercial buildings. I’m sorry that I don’t remember the name. I don’t know if it was a local place or a chain. They served the most heavenly fresh broiled fish, and onion rings in beer batter light as a feather. Dessert was a whopping piece of restaurant made key lime pie. I think of it as one of the top three restaurant meals of my life. It was like finding a diamond ring in a box full of costume jewelry.
I’ve had good food from gas stations. There is a fried chicken franchise called Chesters that seems to always be located in gas stations, and it’s good. Not as good as Popeyes, but we’re grading on a curve here.
Pizza…
I’ve spent my entire adult life (17-54, so far) in New Haven, Connecticut; Manhattan; and Brooklyn. SERIOUS pizza snob.
Last summer I had to drive across North America twice. Oh, god, BAD PIZZA, I was certain.
Delicious pizza in Dayton, eastern Washington State (Chief Springs Pizza and Brewpub) and in Wisdom, Montana, pop. 100, which has one restaurant and one bar. The good pizza was in the bar.
Another great gas station place is the R&R Taqueria in Elkridge, Maryland. You drive to the address and all you see is a gas station. You have to walk around it to see the convenience store next to it. You then have to walk around that to see the tiny diner. It has excellent authentic Mexican food.
I also agree with chappachula that the cafeteria inside of an Ikea is very good.